Signal generator



A/ 0556', L! une l2 1956 c. G` SONTHEIMER ET AL f 2,750504 MHH/JL Filed June 2l, 1951 Bnventor IaRL 6'. JO/YIHEIMER Bg STANLEY l. JAGHS @ma ww; fvzw,

(IttornegS SIGNAL GENERATOR Carl G. Sontheimer, Riverside, and Stanley I. Sachs, Stamford, Conn., assignors to C. G. S. Laboratories, Inc., Stamford, Conn.

Application June 21, 1951, Serial No. 232,752

8 Claims. (Cl. Z50-36) This invention relates to oscillators for generating high frequency electrical curents; More particularly, it re lates to such oscillators which are tunable so that 'they can be Vadjustedvto operate at anyfreqerickyyvridthin a relatively 'wide frequency rangei. i

The tuned circuits of such high frequency generators are usually formed bxgesonanmhambersgrcayities associated with one or more of the tube elements. For example, one resonant cavity may be coupled to the tube plate and another resonant cavity may be'coupled to the control grid or cathode of the tube, suitable feedback to the control element being provided `to produce the desired oscillation.

The resonant frequency of such cavities can be varied by changing the physical dimensions of the cavities. Thus, one wall of the cavity is sometimes formed by a movable plunger having exible contact fingers. By moving the plunger, the size of the cavity and its resonant frequency is varied. K t very hjghfrequencieshforexample ofthe order of three thousand millioncycles peilcond, it is" diiiicul't'u tojiiintainfeiiicient operation at all frequencies within the tuning range.

Moreov'rfii"ismusually necessary to provide two such tunable cavities if the frequency of oscillation is to be varied over a substantial range of frequencies. This makes it tedious to change the frequency of the oscillatorfas itis diiiicult for the operator to make the tw adjustments in such manner as to secure optimum operation at the desired frequency. It is not easy to gang the two tuning adjustments because the extent of movement required to produce a given change in frequency is usually different for the two tuning elements,Y and the likelihoodofspurious modesgfwgscillationfurther vcomplicates the problem. Slch plungers alsowcausemtroubl-ewhen theontacting fingers become dirty QL lgsg their vresiliency so that good cil mimined. A t, "Thewpresent invention overcomes many of these and other disadvantages and is described as embodied inmac compact, wide-Lasse, single C Qattglt tuillilall thatn is simple in const'rtii'kand eflicient in oprtionl Inwapreferred embodiment of the invention, a folded,l .satitymitprayictest and fcharacterlstics of a simple ry the frequency throughout a These and other aspects, objects, and advantages of the invention will be in part pointed out in and in part apparent from the following description of the preferred embodiment of the invention considered in conjunction with the accompanying drawings, in which:

Figure l is a perspective View of a cavity type oscillator embodying the invention; I

Figure 2 is an exploded perspective view showing certain components of the oscillator of Figure 1; and

Figure 3 is an enlarged longitudinal sectional view of the oscillator shown in the preceding drawings.

The oscillator shown in the drawings is adapted for operation in the 3,000 megacycle region and uses a pencl triode tube, generally indicated at 2, for example, of the A2317 series.

nited States Patent O FPice The tube 2 is provided with a cylindrical metal portion 4 through which connection is made to its cathode, the connections to the heater being made through two leads 6 and 8.

In order to provide the folded back resonantgayity for the cathode, a cylindricalre'tal"sleevem,in threaded engagement with an annular metal block 12, is provided with an outwardly extending iiange 14 the outer edge of which is secured to the end of an outer sleeve 16 positioned concentrically around, but spaced from, the internal sleeve 10. An intermediate sleeve 18 is interposed between the sleeves 10 and 16 and is supported at one end by the block 12. The opposite end of the sleeve 18 is spaced from the tiange 14 to provide a folded gavi having a iigsntwcayity portion betyvweerl, tfi'us`l"e-e"v'e'smA 10Ma`nd T8`that opens a acent the iiange Vinto a secondujcavity portrt/lieta @sleeve`s`1`6"andV is. 'This "shdvity portion opens into the annular cavity space between the sleeve 16 and the inner surface of an outer supporting tube 20.

The connection to the planar control grid of the tube 2 is made by means of an annular iiange 22 surrounding the central portion of the tube. A grid sleeve'2ft is secured to the flange 22 by any suitabTTfn'ans; for example, by a ring 25 that is press-fitted into or is in threaded engagement with the iiange 22. This flange 24 extends concentrically within but is spaced from the shell- 20.

Electrical connection is made with the grid sleeve 24 by a spring contact 26 that presses against the outer surface of the grid sleeve. External connection to the grid sleeve contactor 26 can be made by means of a lead 28 that extends through and is insulated from an outwardlyextending metal shield member 32. Fllhgdiameter of the s leadl28 is increased within the tubular shield 32 to fimii desf, ln many cir'tiit"arrange`` Mtrientsfthe grid contac'forwZt can be connected advantageously directly to the shell 20. These or other arrangements can be used, but it is important that some means be provided so that the impedance between the grid contactor 26 and the shell 20 is low at the frequency of operation. l

A metal sleeve 34, which forms part of the tube 2 and is connected to its anode, is connected to a sleeve 36 that forms the inner conductor of the coaxial plate cavity. This s/leeye`36 is provided with contact fingers ,37 that engage the tubevsleeve 34 and at the opposite end is closed and is connected to an electrical conductor 38 by which connection is made between the external electrical circuits and the anode of the tube 2.

The end of the sleeve 36` is maintained at the radio frequency potential of the interior surface of shell 2t) by means of a capacitance sleeve 40. This sleeve is provided at one end with an internal annular flange 42 positioned in face to face relationship with an external annular iiange 44 on the sleeve 36.

The sleeve 40 is maintained in secure electrical contact with the ange 44 and is supported by a number of screws 46 that extend through clearance openings in an insulating supporting block 48 and in the flange 44 into threaded engagement with the ange 42. The capacitance sleeve 40 is spaced from the inner surface of the shell 20 so that the direct plate potential is not applied to the shell 20, but the capacity between the shell 20 and the sleeve 40 is sufficient to maintain the radio frequency potential of the sleeve 40 at the same potential as the interior surface of shell 20. An end cap 50 closes the end of the shell 20 and is maintained in position by screws 52.

In order to permit variation in the frequency of the signal generated by the oscillator, a variable capacitance element, generally indicated at 54, is arranged between the sleeve 36 and the shell 20 and is positioned at a point on the sleeve 36 where there is substantial radio frequency voltage.

A metal plunger 56 is in threaded engagement with the internal surface of a supporting metal tube or sleeve 58 that is secured to the shell 20. The inner end of the plunger 56 is provided with a recessed portion 60 that permits a metal projection 62 on the sleeve 36 to extend within the end of the plunger 56 as the plunger 56 is rotated within the tube 58 so as to move toward the sleeve 36. The change in capacity between the plunger 56 and the projection 62, that is between the sleeve 36 and the shell 20, as the plunger 56 is moved inwardly or outwardly, changes the frequency of operation of the oscillator.

It will be noted that the capacity is predominately between the surfaces of the plunger 56 and the projection 62 that are parallel with the direction of movement of the plunger 56, thus providing a more nearly linear relationship between the frequency and the physical position of the plunger 56 than if the end surface of the plunger 56 were used as one of the capacitive surfaces.

Power is taken from the oscillator by a conventional coupling loop, generally indicated at 64.

With the arrangement described above, the frequency of the signal generated by the oscillator is in the 3,000 megacycle region can be varied as much as 200 to 400 megacycles by adjusting the plunger 56 and without making any other adjustments. Satisfactory power output is maintained throughout the operating range.

It will be noted that the characteristics of the cathode circuit remain unchanged throughout the tuning range.

It will be noted also that the free end of the grid sleeve 24 is directed toward the plate cavity. In practice, this permits a substantially greater tuning range than if the sleeve is directed toward the cathode cavity.

The slots in the sleeve 24 are for the purpose ofwprgeventing @engagements imitegriaslifii;therefr'einwcrease the efticin'cymofu the oscillator. The particular dimensions of the cavities will be selected so that under the existing loading conditions the desired frequency of operation is attained. With the illustrated arrangement, good results have been obtained when the effective length of the cathode cavity is 1.25 wavelengths and the plate cavity is 0.75 wavelength at the center frequency of operation.

From the foregoing, it will be apparent that we have provided a highly useful, high frequency oscillator well adapted to attain the ends and objects heretofore set forth. It will be apparent to those skilled in this'field that various changes and modifications may be made in the illustrated embodiment to adapt the invention to particular uses without departing from the scope of the invention as set forth in the following claims.

What is claimed is:

l. A high frequency tunable oscillator adapted` to utilize a tube having a cathode, a control grid, and an anode compris'ng a first folded cavity type resonant circuit, means for conductively connecting said first cavity to the cathode of said tube, a second .coaxial Itype cavity having an inner and outer conductor, meanfor coupling said second cavity to the anode of said tube, a first ovable conductive capacitive tuning element mounted on gne of said conductors, and a fixed capacitive elementbrounted on the other of said conductors, one of said capacitive elements having a recess therein adapted to receive a portion of the other capacitive element.

2. A high frequency tunable oscillator adapted to utilize a tube having a cathode, a control grid, and an an- The disclosed folded cavity has been found to' have the desired characteristics for permitting this un-I usually wide tuning range.

ode comprising a first folded back cavity type resonant circuit, means conductively connecting said first cavity resonant circuit to the cathode of said tube, a second coaxial type cavity circut having an inner and outer conductor, means for coupling said second cavity circuit to the anode of said tube, and first and second conductive capacitive tuning elements mounted, respectively, on said conductors, said capacitive elements being relatively movable transversely, of said second cavity in spaced overlappihg'ieltionship.

3. A high frequency tunable oscillator adapted to utilize a pencil-type tube having a cathode, a control grid, and an anode comprising a iirst folded cavity type resonant circuit, means for coupling said rst cavity to the cathode of said tube, a second coaxial type cavity circuit having an inner and outer conductor, means for coupling said second cavity to the anode of said tube, a first movable conductive capacitive tuning element mounted on one of said conductors, and a fixed capacitive element mounted on the other of said conductors, one of said capacitive elements having a recess therein adapted to receive a portion of the other capacitive element, a metallic shell forming part of each of said cavifties, a sleeve member positioned concentrically within and closely spaced from said shell, said sleeve member substantially dividing said first and second cavities from each other, and means for connecting said sleeve to said grid.

4. A high frequency tunable oscillator adapted to utilize a tube having a cathode, a control grid, and an anode comprising a first folded cavity type resonant circuit, means for physically connecting said first cavity directly to the cathode of said tube, a second coaxial type cavity having an inner and outer conductor, means for coupling said second cavity to the anode of said tube, and a variable capacitor mounted on said outer conductor of said second cavity and having a conductive element movably mounted relative to said inner conductor for varying the`frequency of operation.

5. A high frequerfty tunable oscillator adapted to utilize a tube having a cathode, a control grid, and an anode comprising a rst folded cavity type resonant circuit, said first cavity communicating directly with the cathode of said tube, a second coaxialrtype Ncavity having an inner and outer conductor, means for coupling said second cavity to the anode of said tube, a conducting member effectively substantially completely separating said folded cavity type resonant circuit from said coaxial type cavity, means for coupling said member to the grid of said tube, and a variable capacitor connected between the inner and outer conductors of said second cavity for varying the frequency of operation,

6. A high frequency tunable oscillator adapted to utilize a tube having a cathode, a control grid, and an anode comprising a first folded cavity type resonant circuit, means defining a passage electromagnetically coupling said first cavity directly to the cathode of said tube, a second coaxial type cavity circuit having an inner and outer conductor, the effective electrical length of said second cavity being equal to approximately sixtenths the effective electrical length of said rst cavity, means for coupling said second cavity to the anode of said tube, electrically conductive means effectively substantially completely separating said tirst and second cavity resonant circuits, and a variable capacitor connected between the inner and outer conductors of said second cavity for varying the frequency of operation.

7, A high frequency tunable oscillator adapted to utilize a tube having a cathode, a control grid, and an anode comprising a iirst folded cavity type resonant circuit, means for physically directly connecting said first cavity to the cathode of said tube, a second coaxial type cavity circuit having an inner and outer conductor, the effective electrical length of said second cavity being equal to approximately six-tenths the effective electrical length of said first cavity, means for coupling said second cavity to the anode of said tube, a variable capacitor connected between the inner and outer conductors of said second cavity for varying the frequency of operation, and screw means for adjusting said capacitor. Vf. A high frequency tunable oscillator adapted to utilize a tube having a cathode, a control grid, and an anode comprising a tgldedfbacl5-wavity,yperesonantmcircuit including an outer cylindrical conductive shell, a first conductive sleeve within said shell defining a first annular cavity portion between said shell and first sleeve, a second conductive sleeve within said irst sleeve defining a second annular cavity portion between said first and second sleeves, said second cavity portion communicating near one end with said first cavity portion near one of its ends, and a third conductive sleeve within said second sleeve defining a third annular cavity portion between said second and third sleeves, said third cavity portion communicating near one end with said second cavity portion near the opposite end from that which communicates with said first cavity portion, said third sleeve being coupled to the cathode of said tube, a sec- 'ond coaxial type cavity having an inner conductor and f an outer conductor, means for coupling said second cavity'to the anode of said tube, a conducting member substantially dividing said coaxial type cavity from said folded-back cavity type resonant circuit, and first and second conductive capacitive tuning elements mounted, respectively, on said conductors, said capacitive elements being relatively movable transversely of said second coaxial-type cavity in spaced overlapping relationship.

References Cited in the file of this patent UNITED STATES PATENTS 2,428,622 Gurewitsch Oct. 7, 1947 2,434,115 McArthur Jan. 6, 1948 2,458,650 Schreiner Jan. 11, 1949 2,462,866 Hotine Mar. 1, 1949 2,476,725 Gurewitsch July` 19, 1949 2,484,562 Gardiner Oct. 1, 1949 2,523,122 Kuper Sept. 19, 1950 2,525,452 Guerwitsch Oct. 10, 1950 2,561,727 Cooper et al. July 24, 1951 2,589,246 Grimm Mar. 18, 1952 2,626,355 Hoffman Ian. 20, 1953 

